Bug 51493

Created attachment 63541 [details]
second testdisplay -m (can't light up)

Test with the combined revert patch.
Prefer mode(2560x1600) still can’t light up for the second time with DP external display connected.

Can you please attach dmesg with drm.debug=0xe after the screen has failed to light up for the second time (but please ensure that dmesg contains everything, including the first time we light up the dp screen and the boot messages).

Created attachment 63750 [details]
dmesg

Hmm, a month old already. Any chance we can dig out a bisect for this and shame the guilty party?

Also, retesting on latest dinq would be very interesting since we've merged two dp link training fixes (train harder from Paulo and prefer wide&slow from Jesse).

We try to bisect and the result show that b2094ef840697bc8ca5d17a83b7e30fad5f1e9fa is the first bad commit. But b2094ef840697bc8ca5d17a83b7e30fad5f1e9fa is a merge commit. 
Then I test with the parent commits and i found that both 424a6f6 and 6681bc0 are good commits. 

commit b2094ef840697bc8ca5d17a83b7e30fad5f1e9fa  424a6f6ef990b7e9f56f6627bfc6c46b493faeb4  6681bc0deba495fad0d6fb349e40524abd1b1732
Merge: 424a6f6 6681bc0
Author: Linus Torvalds <torvalds@linux-foundation.org>
Date:   Thu Mar 22 13:00:13 2012 -0700

So now I’m a little confused, is it possible that the merge commit is a bad commit, even the parent commits are all good commits?

Certainly possible, albeit it doesn't happen often. If this really is the case it means some slight changes in the timing are causing this issue ... which makes it very hard to debug.

Keith is already fighting similar issues where a pipe doesn't light up, but only on 3-pipe configurations. Can you please attach the output of testdisplay -i, too?

Kernel: (drm-intel-testing)ef6113ad0f406db4fbe2bcf3359dd938a6046d75

This bug can also be reproduced, just like Du Yan described.

Kernel: (drm-intel-testing)c3c3d4e9c2daeca01c42040cda0e5e0579c5c80b


mode(2560x1600) can’t light up for the second time with DP mode can also reproduced.

Please test the patch at:

https://patchwork.kernel.org/patch/1446781/

System Environment:
--------------------------
Platform: Ironlake
Kernel: (drm-intel-next-queued)036223401d50594c35fc5f7eafdbd2ddbe3ec921
Some additional commit info:
Author: Lekensteyn <lekensteyn@gmail.com>
Date:   Tue Jun 26 00:36:24 2012 +0200


I build the latest kernel include /patch/1446781/, and this issue disappeared.

Fix merged to dinq as

commit b060990ee7b3d900495a2aabb0ba4f3595d21314
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Wed Sep 12 23:24:09 2012 +0200

    drm/i915: rip out early dp port write for gm45/ilk

System Environment:
-------------------------------
Platform: Ironlake
Kernel: (drm-intel-nightly)2fc764a311ca1e51c69ac3ff2872ae49617f9b46
Some additional commit info:
Merge: 1a9a08f 3d840a1
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Fri Sep 14 23:27:47 2012 +0200


It could light up correctly, can't reproduce this issue.

A patch referencing this bug report has been merged in Linux v3.7-rc1:

commit fba92150aa9959b8f1fa39455315f5e8c59bb702
Author: Daniel Vetter <daniel.vetter@ffwll.ch>
Date:   Wed Sep 12 23:24:09 2012 +0200

    drm/i915: rip out early dp port write for gm45/ilk

Closing old verified.